JPH06212227A - Method for melting iron scrap - Google Patents

Abstract

PURPOSE:To provide a method for economically producing a large quantity of molten iron while preventing the envirnmental problem by using the molten iron together with scrap as iron raw material. CONSTITUTION:On the way of flowing passage for flowing the molten iron 7, a place for heating by arc is arranged, and the iron scrap 6 is fed in there to execute melting. The molten iron quantity discharged from the flowing passage, is adjusted by the molten iron quantity fed into the flowing passage, C concn. in the molten iron discharged from the flowing passage is adjusted so as to be 2.5-3.9%. Further, the gas generated at the time of heating the iron scrap by arc, is fed into the space in the flowing passage for flowing the molten iron, and heating combustion is executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing molten iron in a large amount economically and while solving environmental problems by using hot metal and scrap together as iron raw materials.

[0002]

2. Description of the Related Art Conventionally, iron and steel have been separately manufactured by an integrated iron manufacturing method using molten pig iron as a main raw material manufactured in a blast furnace or the like, and an electric furnace method that melts scrap. However, the amount of scrap generated has increased recently, and 50% of the iron raw material
It's getting closer. This in itself is C when manufacturing steel
Although it is advantageous in terms of reducing the amount of O ₂ generated, when scrap is used, the circulation of impurities such as Trump elements and the effect of the organic gas derived from oil, paint, plastics accompanying the scrap on the environment, etc. It has been found that there are problems, and it is not possible to solve it by melting the increased amount of scrap by the conventional electric furnace method.

Until now, there has been known a method in which molten iron produced in a blast furnace or the like is charged into an electric furnace and melted while adding scrap. However, in such a method, it is included in scrap. Even if the Trump element has a diluting effect, the essential problems of the electric furnace, such as the problem of exhaust gas, remain. Also, there is a method of electrically heating in a hot metal furnace to raise the temperature of the hot metal, but the amount of electric power applied is limited and is not suitable for the purpose of using a large amount of scrap.

[0004]

As described above, in a situation where about 50% pig iron and about 50% scrap are used as iron raw materials, a large amount of molten iron can be economically produced, and environmental problems can be solved at the same time. Since the method is unprecedented, the present invention seeks to provide a method that enables this.

[0005]

As a result of various studies in view of such circumstances, the present invention can achieve the above object by combining the hot metal and scrap melting by electric heating by specifying the conditions as follows. all right. That is, (1) a method for melting iron scrap, characterized in that a place for heating by an arc is provided in the middle of the flow path of the hot metal, and the iron scrap is charged into the place to melt the iron scrap. In the above method (1), the amount of molten metal discharged from the flow channel is adjusted by the amount of hot metal charged into the flow channel,
(3) In the method of (1) or (2) above, the concentration of C in the molten metal discharged from the flow path is adjusted to be 2.5 to 3.9%. Melting method, (4) In the method of (1) or (2) or (3) above, the gas generated when the iron scrap is heated by the arc is sent to the space in the flow path of the hot metal,
A method for melting iron scrap, characterized in that the gas is heated and burned.

[0006]

In the case where the apparatus shown in FIG. 1 is used as an example,
Embodiments of the present invention will be described in detail. Reference numeral 1 is a hot metal supply device. The molten pig iron that has been transported from a smelting furnace by a torpedo car, for example, is supplied to the subsequent process through the apparatus 1. If necessary, oxidation refining such as hot metal dephosphorization is performed in this apparatus. A device 2 for electrical (arc) heating and scrap melting is connected to this device through a hot metal flow path. Here, scrap is melted while always holding the metal pool required for stable arc heating by the hot metal supplied from the apparatus 1. Even if this apparatus does not tilt, the amount of metal required in the subsequent process can be discharged by adjusting the amount of hot metal supplied from the apparatus 1.

Therefore, the apparatus 2 can use not only an expensive graphite firing electrode but also a Zedaberg type self-firing electrode as the electrode. Further, in the device 2, it is not necessary to completely melt the scrap within a certain time. Therefore, the packed bed type scrap preheating device 3 can also be attached. Since the gas generated from the scrap melting part (arc heating part) or the scrap preheating device may contain undecomposed organic matter gas, it is sent to the space of the hot metal supply device 1 to oxidize oxygen or air into the atmosphere. Blow a volatile gas, burn it completely, and then discharge it outside the furnace. By setting the gas temperature in the furnace to 1200 ° C. or higher, it is possible to completely decompose the organic substance gas.

The C concentration of the molten metal in the apparatus 2 is 2.5 to
Adjust to within 3.9%. If C is lower than this, it will be disadvantageous in desulfurizing the metal in the apparatus 2, the amount of heat generated in the subsequent decarburization furnace will be reduced and the scrap digestion amount will be reduced, and the nitrogen in the molten steel after decarburization will be reduced. It is disadvantageous in terms of high concentration. On the other hand, if the C concentration is higher than the above range, the scrap melting rate is rather lowered, which is not preferable. In order for the C concentration of the metal to satisfy the above conditions, coke is added in the furnace. CaO / SiO ₂ generated in the apparatus 2 by this coke is 1.5 to 2.
The slag T. 5 range. It is desirable to reduce Fe to 0.8% or less so that desulfurization can be advantageously performed. The molten metal produced by the apparatus 2 is charged into a subsequent decarburizing furnace, for example, a normal converter, and is subjected to an oxidation reaction such as decarburization and dephosphorization, and a denitrification reaction accompanying it.

As described above, the present invention has the following features, unlike known methods. By connecting a hot metal supply device and a furnace for arc heating with a hot metal flow path, molten metal is supplied to the portion for arc heating so that arc heating can be performed steadily. This means that arc heating can be performed with maximum power and flicker can be reduced, and a large electric furnace has a large effect of reducing the equipment cost for reducing flicker.
The molten metal supply required from the subsequent process is supplied to the device 2
The operation can be performed by controlling the hot metal supply amount without interrupting the operation or tilting the equipment. This means that inexpensive self-baking electrodes can be used as arc heating electrodes and that a scrap preheating device can be installed, which means that equipment costs and operating costs can be reduced, and energy efficiency and productivity can be increased. . Organic matter gas, which is generated when scrap is heated and is a problem, can be decomposed by completely burning it in the space inside the hot metal feeder.

[0010]

EXAMPLE A molten metal (average C = 3.0 to 3.5%) for two 250t scale converters operating at a pitch of about 30 minutes was prepared as follows by using about 50% blast furnace hot metal and about 50 scrap melting. %
Supplied by Blast furnace hot metal is supplied from a torpedo car through a ladle-like continuous hot metal preliminary dephosphorization device with a lid (supplying quicklime, iron oxide, and oxygen gas) to a device for performing arc melting and scrap melting through a torch. To do. The composition of the original hot metal, the temperature is C = 4.3%, Si =
0.2%, S = 0.02%, P = 0.1%, 1380 ° C
However, after the hot metal treatment, C = 4.0%, Si = 0.
06%, S = 0.008%, P = 0.015%, 131
It reached 0 ° C.

The arc heating is carried out by using a self-baking electrode of the Zedaberg type, and the electric power is 37 per scrap melting amount t.
0kWh was continuously supplied (DC). In the scrap melting device by arc, scrap is supplied to the furnace by mounting the shaft on the bottom (angle, 15 ° on one side) (height,
It was carried out intermittently with a double damper from the ceiling of the arc melting device (3.5 m). The gas discharged from the scrap preheating space is sucked into the space of the hot metal supply device, completely burned with air, and the outlet temperature is 1250 ° C, CO =
It was set to 0.05% or less. Under that condition, the presence of organic gas could not be detected in the exhaust gas.

[0012] The scrap is preheated by the exhaust gas in the upper shaft portion of the arc melting apparatus, and when it enters the arc melting apparatus, it is first partially melted in the space by the arc radiant heat and the high temperature gas, and is further applied to the molten metal bath to Melts while charcoal. Scrap is intermittently supplied so that the height of the scrap can be maintained at 2 m or more depending on the melting amount. Coke was added to the molten metal bath to maintain C = 3.0 to 3.5%. Also, lime and silica were added to this molten layer as a flux, and the basicity = 2.4,
T. Fe = 0.7% slag was made. by this,
70% of sulfur could be removed.

After the melting device, one DC electrode was further charged and the temperature was adjusted by heating so that the temperature of the molten metal in the ladle was kept at 1450 ° C. Immediately after setting the pot for supplying to the converter, approximately 40% of the required metal amount
Was carried out by extrusion by hot metal supply, and thereafter, overflow due to scrap melting was supplied, and finally, hot metal extrusion was performed to adjust to the required amount.

[0014]

INDUSTRIAL APPLICABILITY The present invention is a method capable of economically producing a large amount of molten metal by utilizing the existing equipment conditions of an integrated steel mill in response to changes in the situation of iron raw materials, and also playing cards accompanying scrap use. It is also effective for elemental problems and environmental problems, and has great industrial, economic, and mirror-surface effects.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an example of an apparatus used to carry out the present invention.

Claims (4)

[Claims] 1. A method of melting iron scrap, characterized in that a place for heating by an arc is provided in the middle of a flow path of the hot metal, and iron scrap is charged into the place to melt the iron scrap. 2. The method of melting iron scrap according to claim 1, wherein the amount of molten metal discharged from the flow path is adjusted by the amount of hot metal charged into the flow path. 3. The method according to claim 1 or 2, wherein the molten metal discharged from the flow channel has a C concentration of 2.5 to 3.9%.
The method for melting iron scrap is characterized by adjusting so that 4. The method according to claim 1, 2 or 3, wherein the gas generated when the iron scrap is heated by the arc is fed into the space in the flow path of the hot metal to heat and burn the gas. Method of melting iron scrap.